The george w. Bush presidential library will be dedicated today, in texas, down in dallas. But before that milestone, the former president and first lady sat down with our diane sawyer for a revealing interview, talking about the 2016 race, who he thinks would be a great candidate. And of course, the bombings in boston. Reporter: The terrorism in boston. Yeah. Reporter: Many people have wondered if it took you right back to 9/11, when you heard it. I was deeply concerned that this could have been, you know, another highly-organized attack on the country. And it still may be. I don't know the facts. But I do know that it's really hard to protect the homeland. Those who want to do harm only have to be right one time. And we have to be right 100% of the time. Reporter: We ask about the presidency and his party. What will happen in 2016? Do you have one word for the republican party today? You will exist in the future. Reporter: I thought you were going to say, jeb bush. Well, he would be great. Reporter: Two words. Yeah. He would be a marvelous candidate if he chooses to do so. He doesn't need myel because he knows what it is, which is run. Reporter: Your brother versus hillary clinton? It would be a fantastic photo. I'm fascinated by all of the gossip and stuff that goes on. But the field won't become clear until after the midterms. Reporter: As the museum opens, you are looking out, what are you going to be thinking? How blessed I am. It will be really a chance to see friends from all over the country. And lifelong friends from midland. They will be coming if there's free food. Reporter: And then? Back off the stage? Back off the stage, yeah. Each former president chooses his own path. I've chosen mine. And I'm very comfortable with that decision.

This transcript has been automatically generated and may not be 100% accurate.

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